Updated at 9:16 a.m. ET on Wednesday: The Taliban claimed Tuesday that 18 members of Afghanistan's border police force and local militia had deserted their respective services and joined the "Taliban's Islamic Emirate of Afghanistan" in Nangarhar, a province close to Pakistan.

"After holding a few meetings with local elders...all the 18 policemen and personnel of the local militia agreed and came to us at Surkh Rodh area of Nangarhar province," claimed Taliban spokesman Zabihullah Mujahid.

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He said all the policemen joined the insurgent movement early on Tuesday.

There is no way to verify Taliban claims independently, but the organization supplied a list of the names of the 18 who had allegedly defected.

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Taliban insurgents regularly issue claims of responsibility for attacks and other incidents that are later proved to be false.

In a statement sent to NBC News early on Wednesday, Afghanistan's Ministry of the Interior said the Taliban's claims about the police defections were "baseless and untrue."

However, Mujahid said they had persuaded local elders and parents to convince their sons who were working in the new Afghan security services to stop supporting the "occupying" forces in Afghanistan.

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Many Afghans say the Taliban often threaten family members and relatives of those serving in the Afghan army or police, putting them under pressure to quit.

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Two U.S. service members were killed in an insurgent attack in Afghanistan on Saturday, the NATO-led International Security Assistance Force (ISAF) said.

The attack occurred in the country's eastern Ghazni province, ISAF said, not giving any further details.

ISAF said identification of victims is deferred to the Department of Defense.

In a separate incident early Saturday, two suicide attackers -- one driving a fuel tanker -- blew themselves up near a U.S. base in the eastern Wardak province, killing at least 12 people, officials said.

The violence served as a reminder that even after a decade of fighting, tens of thousands of U.S. and foreign troops are still engaged in a war that shows no signs of slowing down despite the start of a withdrawal of coalition forces.

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The U.S.-led NATO coalition said that no American or coalition troops were killed in the suicide blasts in the town of Sayed Abad, about 40 miles from Kabul. It confirmed that a number of troops were wounded, but did not say how many, in accordance with coalition policy. 

Shahidullah Shadid, a spokesman for the Wardak provincial governor, said one suicide bomber detonated a vest rigged with explosives outside a compound housing the district governor's office as well as local police and Afghan army headquarters. A second bomber driving a fuel tanker detonated his bomb on a road separating the compound from the base.

Shadid said the dead included eight civilians and four Afghan police.

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Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack, which he said was targeting the U.S. base.

Government officials said the first attacker blew himself up to try to eliminate the Afghan security force guarding the compound and clear the way for the truck to hit the base down the road from the governor's complex. The second bomber then blew up the fuel tanker as he was approaching the base. One of the town's main bazaars is also located near the bomb site.

"A small explosion happened followed by a big one caused by a truck," said eyewitness Hamidullah, who like many Afghans goes by one name. "In these explosions a lot of people were wounded and also a large number of shops were destroyed. I fell down on the ground and everything around me was destroyed."

Officials said the second blast was far larger than the first.

"It was a very powerful explosion. It broke windows all over the area," said provincial police chief Gen. Abdul Qayum Bakizai. "Most of the injuries are from broken glass from the windows of homes and shops. It was so powerful we couldn't find much of the truck."

The governor's office said in a statement that 59 people were wounded: two NATO troops, 47 civilians and ten Afghan police officers. 

Slideshow: Afghanistan: Nation at a crossroads

Hoshang Hashimi / AP

More than ten years after the beginning of the war, Afghanistan faces external pressure to reform as well as ongoing internal conflicts.

Launch slideshow

Last year, the same base in Wardak was the target of another suicide bombing. That blast, which occurred on the anniversary of the Sept. 11 terrorist attacks against the United States, wounded 77 American soldiers and killed five Afghans. No U.S. troops were killed when the massive truck bomb exploded outside the base.

The United States and other countries have already begun drawing down their forces in Afghanistan as part of a strategy that aims to hand over security responsibility to the Afghans by the end of 2014, when nearly all foreign troops are set to leave the country. President Barack Obama has pledged to remove 23,000 U.S. troops by the end of September, bringing the number of American forces down to 68,000.

What's leading Afghan troops to turn on coalition forces?

There are currently 129,000 troops serving with the coalition, according to US Maj. Gen. Joseph Reynes Jr., director of operations at the Allied Joint Forces Command in Brunssum, the Netherlands. He said earlier this week that the number will drop to 108,000 by the end of October and dip under 100,000 by the end of the year.

The troops are to be replaced by Afghan army and police units, but many have questioned the effectiveness of an Afghan force that has high desertion rates and is often poorly disciplined. The Afghan security forces are supposed to reach a high of about 350,000 at the end of the year. 

The Associated Press and Reuters contributed to this report.

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KABUL, Afghanistan -- A number of Afghan national army soldiers have been arrested inside the country’s defense ministry over a foiled suicide bomb plot, officials told NBC News.

The soldiers were held on Monday afternoon along with 11 suicide bomb vests in a guard box in the building in the capital, Kabul, army officials said on Tuesday.

Afghan news web site Khaama also reported the arrests, saying the incident raises fresh concerns over infiltration of militants among the country’s Afghan security forces.

There were no further details immediately available.

Tim Marshall, foreign editor of UK channel Sky News, said that the incident was serious, and showed that the Taliban are determined to chase NATO out of the country.

"The fact that these arrests took place within the walls of the defense ministry illustrates the level of insurgent penetration within the Afghanistan establishment and just tells you -- gives a signal of -- what is likely to happen when NATO leaves," he said.

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The arrests came on the same day that at least three NATO service members were shot dead by Afghan security forces in two separate attacks.

A gunman wearing an Afghan army uniform killed two NATO troops in southern Afghanistan, while another was shot in eastern Afghanistan by an alleged member of the Afghan Local Police.

The attacks brought to 16 the number of NATO-led forces killed so far this year in what appeared to be attacks by members of Afghan forces.

Meanwhile, support for the war in Afghanistan has dropped sharply among both Republicans and Democrats, according to a New York Times/CBS News poll published Tuesday.

The survey found that more than two-thirds of those polled — 69 percent — thought that the United States should not be at war in Afghanistan, the New York Times reported.

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Just four months ago, 53 percent said that Americans should no longer be fighting in the conflict, it said.

It added that the increased disillusionment was even more pronounced when respondents were asked their impressions of how the war was going. The poll found that 68 percent thought the fighting was going “somewhat badly” or “very badly,” compared with 42 percent who had those impressions in November.

The poll was conducted by telephone from March 21 to 25 with 986 adults nationwide.

Akbar Shinwari, NBC News in Kabul, and msnbc.com staff also contributed to this report.

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